5 International Journal of GEOMATE, April, 2017, Vol. 12 Issue 32, pp. 5-11 Geotec., Const. Mat. & Env., ISSN:2186-2990, Japan, DOI: http://dx.doi.org/10.21660/2017.32.6556 SOIL BEARING CAPACITY REFERENCE FOR METRO MANILA, PHILIPPINES *Jonathan R. Dungca 1 , Ismael Concepcion Jr. 2 , Moises Christian Mickhail Limyuen 3 , Terence Oliver See 4 and Marion Ryan Vicencio 5 1 Gokongwei College of Engineering, De La Salle University, Philippines *Corresponding Author, Received: 06 June 2016, Revised: 02 August 2016, Accepted: 30 Nov. 2016 ABSTRACT ABSTRACT: This study focuses on the analysis of the soil bearing capacities of the various cities and municipalities of Metro Manila, Philippines. The allowable soil bearing capacities to be used for foundation design were calculated through various theories and studies using geotechnical parameters, such as relative density and angle of internal friction. Standard Penetration Test (SPT) results were used to estimate these geotechnical parameters in order to obtain a good approximation of the soil‘s bearing capacity. Because of economic constraints, not all low-rise construction projects choose to perform soil exploration. Due to this, soil data are usually lacking and may cause problems when designing shallow foundations of these kinds of structures. In line with this kind of situation, the study can help engineers in designing shallow foundations by providing them a reference of the allowable soil bearing capacity of any area within Metro Manila. This will be able to give them a good idea of the soil‘s strength in sup porting shallow foundations. The allowable bearing capacity of the soil shown in the reference is obtained from collected borehole data within Metro Manila and by using several geotechnical engineering theories. Contour maps of the bearing capacities are then made in order to provide an overview of the soil bearing capacity for shallow foundations. A Geographic Information System (GIS) software database was also made so as to store all the borehole location‘s data as well as serving another basis for estimation. This can be updated whenever new data is available. Keywords: Soil Bearing Capacity, Foundation Design, Standard Penetration Test, Geotechnical Properties of Metro Manila INTRODUCTION Foundation design requires engineers to understand how the soil interacts with the foundations. But, foundations are situated underground, wherein engineers cannot explicitly describe the interactions of the soil underground without conducting some tests. As soil exploration is a very costly test to conduct, engineers cannot always perform these tests; therefore, they rely on previous explorations done by their peers that are close to the project site to approximate the value for the soil bearing capacity for the aforementioned. Since soil exploration is too costly and mere guessing will not suffice when making foundations, the author decided to come up with a way to fill in the dire needs of engineers. Using the borehole logs available within the Metro Manila, Philippines, the study analyzed the SPT borehole logs, calculated the required soil parameters and compiled everything into a reference that shows the bearing capacities of the covered areas. The study aims to create a reference that will provide structural engineers the estimated allowable soil bearing capacities at any point in Metro Manila Philippines through the use of contour maps. METHODOLOGY With Metro Manila having an approximate size of 597.47 square kilometers, a density of one borehole log per square kilometer was used to describe the geotechnical characteristics and possible foundation design parameters of the said area. Borehole logs were collected for a total of 486 locations all over Metro Manila. The amount of borehole logs alone is not the only criterion in gathering data for the study. It is just as important as, that the locations of the borehole logs be properly distributed. To check their distribution, each of the locations of the borehole logs was plotted in a map of Metro Manila. After this, the distribution was visually inspected and the areas that needed more data were determined. Aside from these, borehole logs that seemed erroneous were removed and disregarded. In properly designing shallow foundations, the geotechnical characteristics and allowable bearing
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International Journal of GEOMATE, April, 2017, Vol. 12 Issue 32, pp. 5-11 Geotec., Const. Mat. & Env., ISSN:2186-2990, Japan, DOI: http://dx.doi.org/10.21660/2017.32.6556
SOIL BEARING CAPACITY REFERENCE FOR METRO MANILA,
PHILIPPINES
*Jonathan R. Dungca1, Ismael Concepcion Jr.
2, Moises Christian Mickhail Limyuen
3,
Terence Oliver See4 and Marion Ryan Vicencio
5
1Gokongwei College of Engineering, De La Salle University, Philippines
*Corresponding Author, Received: 06 June 2016, Revised: 02 August 2016, Accepted: 30 Nov. 2016
ABSTRACT
ABSTRACT: This study focuses on the analysis of the soil bearing capacities of the various cities and
municipalities of Metro Manila, Philippines. The allowable soil bearing capacities to be used for foundation
design were calculated through various theories and studies using geotechnical parameters, such as relative
density and angle of internal friction. Standard Penetration Test (SPT) results were used to estimate these
geotechnical parameters in order to obtain a good approximation of the soil‘s bearing capacity. Because of
economic constraints, not all low-rise construction projects choose to perform soil exploration. Due to this, soil
data are usually lacking and may cause problems when designing shallow foundations of these kinds of
structures. In line with this kind of situation, the study can help engineers in designing shallow foundations by
providing them a reference of the allowable soil bearing capacity of any area within Metro Manila. This will be
able to give them a good idea of the soil‘s strength in supporting shallow foundations. The allowable bearing
capacity of the soil shown in the reference is obtained from collected borehole data within Metro Manila and by
using several geotechnical engineering theories. Contour maps of the bearing capacities are then made in order to
provide an overview of the soil bearing capacity for shallow foundations. A Geographic Information System
(GIS) software database was also made so as to store all the borehole location‘s data as well as serving another
basis for estimation. This can be updated whenever new data is available.
Keywords: Soil Bearing Capacity, Foundation Design, Standard Penetration Test, Geotechnical Properties of
Metro Manila
INTRODUCTION
Foundation design requires engineers to
understand how the soil interacts with the
foundations. But, foundations are situated
underground, wherein engineers cannot explicitly
describe the interactions of the soil underground
without conducting some tests. As soil exploration is
a very costly test to conduct, engineers cannot
always perform these tests; therefore, they rely on
previous explorations done by their peers that are
close to the project site to approximate the value for
the soil bearing capacity for the aforementioned.
Since soil exploration is too costly and mere
guessing will not suffice when making foundations,
the author decided to come up with a way to fill in
the dire needs of engineers. Using the borehole logs
available within the Metro Manila, Philippines, the
study analyzed the SPT borehole logs, calculated the
required soil parameters and compiled everything
into a reference that shows the bearing capacities of
the covered areas.
The study aims to create a reference that will
provide structural engineers the estimated allowable
soil bearing capacities at any point in Metro Manila
Philippines through the use of contour maps.
METHODOLOGY
With Metro Manila having an approximate size
of 597.47 square kilometers, a density of one
borehole log per square kilometer was used to
describe the geotechnical characteristics and
possible foundation design parameters of the said
area. Borehole logs were collected for a total of 486
locations all over Metro Manila.
The amount of borehole logs alone is not the
only criterion in gathering data for the study. It is
just as important as, that the locations of the
borehole logs be properly distributed. To check their
distribution, each of the locations of the borehole
logs was plotted in a map of Metro Manila. After
this, the distribution was visually inspected and the
areas that needed more data were determined. Aside
from these, borehole logs that seemed erroneous
were removed and disregarded.
In properly designing shallow foundations, the
geotechnical characteristics and allowable bearing
International Journal of GEOMATE, April, 2017, Vol. 12 Issue 32, pp. 5-11
capacity of the soil must be known. This is because
the design would largely depend on the strength and
the behavior of the soil. The bearing capacities are
computed using the SPT N values found in the
borehole logs which were corrected using the
procedures discussed in [1]-[4], also shown in
Equation 1.
𝑁60 =𝐸𝑚𝐶𝐵𝐶𝑆𝐶𝑅𝐶𝑁𝑁
0.6
Where: N60 is the corrected SPT-N value (blows/ft),
Em is the hammer efficiency, CB is the borehole
diameter correction, CS is the sampler correction, CR
is the rod length correction, CN is the overburden
pressure correction and N is the SPT-N recorded in
the field.
The corrected SPT, N60, values were then used to
compute for various geotechnical parameters such as
relative density, undrained shear strength and angle
of internal friction using different correlation factors
[5]-[9]. As such, the group computed the ultimate
soil bearing capacity. The Terzaghi‘s and Vesic‘s
bearing capacity formulas, shown on Equations 2
and 3 respectively, were used to achieve this [10]-
[12].
𝑞𝑢𝑙𝑡 = 1.2𝑐𝑁𝑐 + 𝛾𝐷𝑓𝑁𝑞 + 0.4𝛾𝐵𝑁𝛾
where: qult is the ultimate soil bearing capacity, γ is
the effective unit weight, B is the width of
foundation, Df is the depth of foundation below
ground surface, Nc, Nγ and Nq are the Terzaghi’s
factors.
𝑞𝑢𝑙𝑡 = 𝑐′𝑁𝑐𝑠𝑐𝑑𝑐𝑖𝑐𝑏𝑐𝑔𝑐 + 𝜎𝑧𝐷′ 𝑁𝑞𝑠𝑞𝑑𝑞𝑖𝑞𝑏𝑞𝑔𝑞
+ 0.5𝛾′𝑁𝛾𝑠𝛾𝑑𝛾𝑖𝛾𝑏𝛾𝑔𝛾
Where: sc, sq, sγ are shape factors; dc, dq, dγ are depth